Plasma doping method with gate shutter

ABSTRACT

In a plasma doping device according to the invention, a vacuum chamber is evacuated with a turbo-molecular pump as an exhaust device via a exhaust port while a predetermined gas is being introduced from a gas supply device in order to maintain the inside of the vacuum chamber to a predetermined pressure with a pressure regulating valve. A high-frequency power of 13.56 MHz is supplied by a high-frequency power source to a coil provided in the vicinity of a dielectric window opposed to a sample electrode to generate inductive-coupling plasma in the vacuum chamber. A high-frequency power source for supplying a high-frequency power to the sample electrode is provided. Uniformity of processing is enhanced by driving a gate shutter and covering a through gate.

RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.11/887,323, filed on Feb. 13, 2009, which is the U.S. National Phaseunder 35 U.S.C. §371 of International Application No. PCT/JP2006/306561,filed on Mar. 29, 2006, which in turn claims the benefit of JapaneseApplication No. 2005-099149, filed on Mar. 30, 2005, the disclosures ofwhich Applications are incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a plasma doping method for introducingimpurities into the surface of a solid sample such as a semiconductorsubstrate and a plasma-processing device for plasma-processing a sample.

BACKGROUND ART

As a technique to introduce impurities into a solid sample, the plasmadoping method is known for ionizing impurities and introducing theionized impurities into a solid with low energy (for example, refer toPatent Reference 1). FIG. 9 shows a general configuration of aplasma-processing device used for the plasma doping method as a relatedart impurity introducing method described in the Patent Reference 1. InFIG. 9, a sample electrode 6 for mounting a sample 9 composed of asilicon substrate is provided in a vacuum chamber 1. In the vacuumchamber 1 are provided a gas supply device 2 for supplying a doping rarematerial gas such as B₂H₆ and a pump 3 for depressurizing the inside ofthe vacuum chamber 1 in order to maintain the inside of the vacuumchamber 1 at a constant pressure. Microwaves are radiated from amicrowave waveguide 41 into the vacuum chamber 1 via a quartz plate 42as a dielectric window. Interaction of the microwaves and the DCmagnetic field formed by an electromagnet 43 forms high magnetic fieldmicrowave plasma (electron cyclotron resonance plasma) 44 in the vacuumchamber 1. To the sample electrode 6 is connected a high-frequency powersource 10 via a capacitor 45 so as to control the potential of thesample electrode 6. Gas supplied from a gas supply device 2 isintroduced into the vacuum chamber 1 from gas flow-out holes 46 and isexhausted into a pump 3 from an exhaust port 11.

In a plasma processing device thus configured, a doping raw material gasintroduced from the gas inlet 46, for example B₂H₆ is turned into plasmaby way of plasma generating means including the microwave waveguide 41and the electromagnet 43 and boron ions in the plasma 44 is introducedinto the surface of the sample 9 by way of the high-frequency powersource 10.

After a metallic wiring layer is formed on the sample 9 on whichimpurities have been introduced, a thin oxide film is formed on themetallic wiring layer in a predetermined oxidizing atmosphere and then adate electrode is formed on the sample 9 by using a CVD device or thelike to obtain a MOS transistor, for example.

In the field of a general plasma-processing device, a plasma processingdevice including a gate shutter is known (for example, refer to PatentReference

2). FIG. 10 shows the general configuration of a related art dry etchingdevice described in Patent Reference 2. In FIG. 10, a sample istransferred into the vacuum chamber 1 via the through gate (gatepassage) 51 of the vacuum chamber 1 and then the sample is mounted onthe sample electrode 6 in the vacuum chamber 1 and plasma processing ismade on the sample in the vacuum chamber 1. A reaction chamber 1 as avacuum chamber includes a cover 52 for preventing the reactive productsfrom being built up on the gate passage 51 by covering an opening at thereaction chamber as an opening of the gate passage 51 in the reactionchamber when a semiconductor wafer as a sample is processed in thereaction chamber 1 as a vacuum chamber. The cover 52 includes ashielding plate 53 and a base seat 54 on which the shielding plate 53 ismounted. The shielding plate 53 is a belt-like thin plate formed alongthe inner wall 1 b of the reaction chamber 1 and having a widthdimension larger than the width dimension of the opening at the reactionchamber so as to cover the entire opening at the reaction chamber. Anumeral 55 represents a preliminary chamber, 56 a gate valve, 57 atransfer arm, and 58 a driving device. (Description of a component withan asterisk (*) is omitted.)

-   Patent Reference 1: U.S. Pat. No. 4,912,065-   Patent Reference 2: JP-A-10-199957

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

The related art has a problem of poor uniformity of introduction amount(dose) of impurities into a sample plane. The gas flow-out holes 46 arearranged anisotropically so that the dose is large in a position closeto the gas flow-out holes 46 and small in a position distant from theflow-out holes 46. Another problem is variations in the dose caused bythe influence of a through gate (not shown).

Thus, an attempt has been made to perform plasma doping by using aplasma processing device described in Patent Reference 2 with the resultthat particles are generated when a gate shutter is driven.

The invention has been accomplished in view of the above circumstances.An object of the invention is to provide a plasma doping methodexcellent in the uniformity of concentration of impurities introduced inthe surface of a sample and a plasma-processing device capable ofuniformly performing plasma processing of a sample.

Means for Solving the Problems

The invention provides a plasma doping method comprising steps of:transferring a sample into a vacuum chamber via the through gate of thevacuum chamber; mounting the sample on a sample electrode in the vacuumchamber; evacuating the inside of the vacuum chamber while flowing a gastoward the sample almost isotropically from a surface opposed to thesample; generating plasma in the vacuum chamber while controlling theinside of the vacuum chamber at a predetermined pressure; and causingimpurity ions in the plasma to collide with the surface of the sample tointroduce the impurity ions into the surface of the sample; wherein thethrough gate is covered with a gate shutter when plasma is generated.

With this arrangement, it is possible to provide a plasma doping methodexcellent in the uniformity of concentration of impurities introducedinto the sample surface.

The plasma doping method according to the invention preferably generatesplasma in a vacuum chamber by supplying a plasma source with ahigh-frequency power. With this arrangement, it is possible to performplasma doping at high speed while maintaining the uniformity ofimpurities introduced into the surface of the sample.

The plasma doping method according to the invention is an especiallyuseful plasma doping method in case the sample is a semiconductorsubstrate made of silicon. The plasma doping method is especially usefulin case the purities are arsenic, phosphorus, boron, aluminum, orantimony.

With this arrangement, it is possible to manufacture an ultrafinesilicon semiconductor device.

The invention provides a plasma processing device comprising: a vacuumchamber; a sample electrode; a gas supply device for supplying gas intothe vacuum chamber; gas flow-out holes arranged isotropically whileopposed to the sample electrode; an exhaust port for evacuating theinside of the vacuum chamber; a pressure controller for controlling thepressure inside the vacuum chamber; and a sample electrode power sourcefor supplying power to the sample electrode; wherein the vacuum chamberincludes a through gate and a gate shutter including a driving devicemovable between an open position where the through gate is opened and aclose position where the through gate is covered.

With this arrangement, it is possible to provide a plasma-processingdevice capable of uniformly performing plasma processing on a sample. Inparticular, uniform plasma doping is made possible.

In the plasma-processing device according to the invention, the gateshutter preferably has a cylindrical shape. With this arrangement, it ispossible to uniformly process a circular sample.

The vacuum chamber preferably has a cylindrical shape. With thisarrangement, it is possible to uniformly process a circular sample.

The plasma-processing device preferably includes a cylindrical innerchamber fixed to the vacuum chamber inside the gate shutter. With thisarrangement, it is possible to enhance the wet maintainability of thedevice.

The lowermost part of the inner chamber is preferably positioned belowthe lowermost part of the gate shutter. With this arrangement, it ispossible to enhance the wet maintainability of the device.

The lowermost part of the inner chamber is preferably positioned belowthe upper surface of the sample electrode. With this arrangement, it ispossible to enhance the wet maintainability of the device.

The driving device preferably includes a motor, a rotary body inintimate contact with the gate shutter, and a transmission part fortransmitting the rotary motion of the motor to the rotary body. Withthis arrangement, it is possible to smoothly drive the gate shutter.

The rotary body is preferably made of an elastic resin. With thisarrangement, it is possible to prevent generation of particles caused byrotation of the gate shutter.

The inner chamber is preferably fixed to the vacuum chamber by placing ahood part projecting outside the cylinder on the upper surface of thevacuum chamber. With this arrangement, it is possible to preventgeneration of particles caused by rotation of the gate shutter.

The inner chamber and the gate shutter are preferably coupled to eachother with a cylindrical bearing unit. With this arrangement, it ispossible to smoothly rotate the gate shutter.

The plasma-processing device preferably includes the bearing unit ineach of two positions, an upper position and a lower position. With thisarrangement, it is possible to prevent generation of particles caused byrotation of the gate shutter.

Preferably, the inner periphery of a convex part projecting inside thecylinder of the gate shutter is fitted to a concave part providedoutside the cylinder of the inner chamber, the bearing unit is providedbetween the convex part and the concave part, and the inner diameter ofthe convex part is smaller than the external shape of the cylinder ofthe inner chamber. With this arrangement, it is possible to preventgeneration of particles caused by rotation of the gate shutter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a plasma-doping chamber used in thefirst embodiment of the invention.

FIG. 2 is a plan view of a dielectric window according to the firstembodiment of the invention.

FIG. 3 is a cross-sectional view of a driving device according to thefirst embodiment of the invention.

FIG. 4 is a cross-sectional view of a plasma-doping chamber used in thesecond embodiment of the invention.

FIG. 5 is a cross-sectional view of a link part of an inner chamber anda gate shutter according to the third embodiment of the invention.

FIG. 6 is a cross-sectional view of a plasma-doping chamber used in thefourth embodiment of the invention.

FIG. 7 is a perspective view of an inner chamber and a gate shutter usedin the fourth embodiment of the invention.

FIG. 8 is a perspective view of the inner chamber and the gate shutterused in the fourth embodiment of the invention.

FIG. 9 is a cross-sectional view of a plasma-doping device used in arelated art example.

FIG. 10 is a cross-sectional view of a dry etching device used in therelated art example.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

-   -   1: Vacuum chamber    -   2: Gas supply device    -   3: Turbo-molecular pump    -   4: Pressure regulating valve    -   5: High-frequency power source for a plasma source    -   6: Sample electrode    -   7: Dielectric window    -   8: Coil    -   9: Substrate    -   10: High-frequency power source for a sample electrode    -   11: Exhaust port    -   12: Support    -   13: Gas introduction path    -   14: Gas main path    -   15: Gas flow-out hole    -   16: Through gate    -   17: Inner chamber    -   18: Gate shutter    -   19: Driving device

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the invention will be described referring to drawings.

Embodiment 1

Embodiment 1 of the invention will be will be described referring toFIGS. 1 to 3.

FIG. 1 is a cross-sectional view of a plasma-doping device used in thefirst embodiment of the invention. In FIG. 1, a vacuum chamber 1 isevacuated with a turbo-molecular pump 3 as an exhaust device while apredetermined gas is being introduced from a gas supply device 2 inorder to maintain the inside of the vacuum chamber 1 to a predeterminedpressure with a pressure regulating valve 4. A high-frequency power of13.56 MHz is supplied by a high-frequency power source 5 to a coil 8 (across-section thereof is shown in FIG. 1) provided in the vicinity of adielectric window 7 opposed to a sample electrode 6 to generateinductive-coupling plasma in the vacuum chamber 1. A silicon substrate 9as a sample is mounted on the sample electrode 6. A high-frequency powersource 10 for supplying a high-frequency power to the sample electrode 6is provided. The high-frequency power source 10 functions as a voltagesource for controlling the potential of the sample electrode 6 so thatthe substrate 9 as a sample will have a negative potential with respectto the plasma. This makes it possible to accelerate ions in the plasmatoward the surface of the sample and introduce impurities into thesurface of the sample. Gas supplied from the gas supply device 2 isexhausted from the exhaust port 11 to the pump 3. The turbo-molecularpump 3 and the exhaust port 11 are arranged just below the sampleelectrode 6. The pressure regulating valve 4 is an elevating valvearranged just below the sample electrode 6 and just above theturbo-molecular pump 3. The sample electrode 6 is a base seat of anearly square shape on which the substrate 9 is mounted and is fixed tothe vacuum chamber 1 at each side via total four supports 12.

A flow controller (mass flow controller) provided in the gas supplydevice 2 controls the flow of gas including an impurity material gas. Ingeneral, a gas obtained by diluting an impurity material gas withhelium, for example, a gas obtained by diluting diborane (B₂H₆) withhelium (He) up to 0.5% is used as an impurity material gas, which issubjected to flow control by a first mass flow controller. Flow controlof helium is made by a second mass flow controller. Gasesflow-controlled by the first and second mass flow controllers are mixedwith each other in the gas supply device 2 and the resultant mixture gasis guided into the gas main path 14 via piping (gas introduction path)13. The mixture gas is guided into the vacuum chamber 1 from gasflow-out holes 15 via a plurality of holes communicated with the gasmain path 14. The plurality of gas flow-out holes 15 flow-out gas towardthe sample 9 from a surface opposed to the sample 9.

FIG. 2 is a plan view of a dielectric window 7 in FIG. 1 as seen fromthe bottom. As understood from FIG. 2, the gas flow-out holes 15 arearranged almost symmetrically about the center of the dielectric window7 to flow-out gas almost isotropically toward a sample. In other words,the plurality of gas flow-out holes 15 are arranged almostisotropically.

In FIG. 1, the vacuum chamber 1 is almost cylindrical. The vacuumchamber 1 includes a through gate 16 and a cylindrical inner chamber 17fixed to the vacuum chamber 1. The inner chamber 17 is fixed to thevacuum chamber 1 by placing a hood part projecting outside the cylinderon the upper surface of the vacuum chamber 1. The vacuum chamber 1 alsoincludes a cylindrical gate shutter 18 movable between an open positionwhere the through gate 16 is opened and a close position where thethrough gate is covered. The moving motion is a rotary motion driven bya driving device 19. The inner chamber 17 is arranged inside the gateshutter 18. The inner chamber 17 and the gate shutter 18 are coupled toeach other with a cylindrical bearing unit 20.

The lowermost part of the inner chamber 17 is positioned below thelowermost part of the gate shutter 18. Further, the lowermost part ofthe inner chamber 17 is positioned below the upper surface of the sampleelectrode 6.

FIG. 3 is a cross-sectional view of the driving device 19. In FIG. 3,the inner chamber 17 and the gate shutter 18 are coupled to each otherwith the cylindrical bearing unit 20. While the bearing unit 20 is notshown in detail in FIG. 3, the bearing unit 20 includes an innercylinder, an outer cylinder and a bearing. The inner cylinder is fixedto the inner chamber 17 and the outer cylinder is fixed to the gateshutter 18. This arrangement makes it possible to arbitrarily change therelative positions of the inner chamber 17 and the gate shutter 18concerning a coaxial motion. The gate shutter 18 has a rotary body 21made of an elastic resin (a chemical-resisting resin such as VITON® orKALREZ®) adhering thereto. The rotary body 21 is fixed to a spindle 22and a small gear 23 is fixed to almost center of the spindle 22. A largegear 24 coupled to the small gear 23 is provided and is connected to amotor shaft 27 via a shaft 25 and a trapezoidal gear 26. When a motor 28is operated, its rotary motion is transmitted to the rotary body 21 viaa transmission part including the motor shaft 27, the trapezoidal gear26, the shaft 25, the large gear 24, the small gear 23 and the shaft 22thus allowing the relative positions of the inner chamber 17 and thegate shutter 18 to be arbitrarily changed concerning the coaxial motion.

With the gate shutter 18 placed in an open position, a sample 9 istransferred into the vacuum chamber 1 via the through gate 16 of thevacuum chamber 1. Next, the sample 9 is mounted on the sample electrode6 in the vacuum chamber 1. Then the through gate 16 is covered with thegate shutter 18. That is, the driving device 19 is driven to rotate thegate shutter 18 coaxially with the inner chamber 17 to move the gateshutter into the close position. The inside of the vacuum chamber 1 isevacuated while flowing out gas almost isotropically toward the sample 9from a surface opposed to the sample 9. The inside of the vacuum chamber1 is controlled at a predetermined pressure level and plasma isgenerated in the vacuum chamber 1. Impurity ions in the plasma arecaused to collide with the surface of the sample 9 to introduce theimpurity ions into the surface of the sample 9. To be more specific,with the temperature of the sample electrode 6 maintained at 25° C., theB₂H₆ gas diluted with He as well as the He gas are supplied by 5 sccmand 100 sccm respectively into the vacuum chamber 1. With the pressureinside the vacuum chamber 1 maintained at 0.5 Pa, a high-frequency powerof 1300 W is supplied to a coil 8 to generate plasma in the vacuumchamber 1. At the same time, a high-frequency power of 250 W is suppliedto the sample electrode 6 to cause boron ions in the plasma to collidewith the surface of the substrate 9 thereby introducing the boron in thevicinity of the surface of the substrate 9. The intra-plane uniformityof concentration (dose) of boron introduced in the vicinity of thesurface of the substrate 9 is an excellent ±0.95%. When the sample 9 istransferred out of the vacuum chamber 1, the driving device 19 isdriving again to rotate the gate shutter 18 coaxially with the innerchamber 17 to move the gate shutter 18 into the open position.

For comparison, processing under the same conditions except that thegate shutter 18 is maintained in the open position has shown a poorintra-plane uniformity of dose. Just after the wet maintenance of theinner chamber 17 and the gate shutter 18, the dose near the through gate16 is large (±1.8%). The dose near the through gate 16 is small (±3.4%)after several hundreds of wafers have been processed. The dose near thethrough gate 16 is large again (±2.8%) after several thousands of wafershave been processed.

Possible causes for such results will be discussed. Just after the wetmaintenance, no boron deposits exist on the inner walls of the innerchamber 17 and the gate shutter 18. The inner wall surface of thethrough gate 16 is remote from the plasma so that accumulation of borondeposits progresses more slowly than in other regions. The amount perunit time of boron radicals lost from a vapor phase is smaller in aregion close to the through gate 16 than elsewhere. Thus, theconcentration of boron radicals in the plasma is large and the dose isaccordingly large near the through gate 16.

The result obtained after several hundreds of wafers have been processedwill be discussed. In this stage, a considerable amount of borondeposits are accumulated on the inner wall surfaces of the inner chamber17 and the gate shutter 18. As discussed above, Boron deposits areaccumulated faster in a region remote from the through gate 16. Sincethe absorption probability of boron radicals drops as the depositsincrease, the deposit amount is saturated earlier in a region remotefrom the through gate 16. Little amount of boron radicals is absorbed ina region remote from the through gate 16. Thus the concentration ofboron radicals in plasma is higher and the dose is larger in a regionremote from the through gate 16.

The result obtained after several thousands of wafers have beenprocessed will be discussed. In this stage, a considerable amount ofboron deposits are accumulated and saturated on the inner wall surfacesof the inner chamber 17 and the gate shutter 18 as well as the throughgate 16. In other words, the absorption probability of boron radicals ina portion inside the vacuum chamber 1 exposed to plasma is low in anylocation. The inner wall surface of the through gate 16 has a largersurface area exposed to plasma than elsewhere. Thus, boron radicalsgenerated by detachment from the deposits increases, that is, the doseincreases in a region close to the through gate 16.

According to this embodiment, the nonuniformity of dose describe aboveis successfully eliminated by moving the gate shutter 17 into a closeposition.

In Embodiment 1, the gate shutter 18 is cylindrical. This arrangementallows uniform processing of a circular sample. The vacuum chamber 1 hasa cylindrical shape.

With this arrangement, the circular sample 9 is uniformly processed. Thecylindrical inner chamber 17 fixed to the vacuum chamber 1 is arrangedinside the gate shutter 18. This arrangement enhances the wetmaintainability of the device. The lowermost part of the inner chamber17 is positioned below the lowermost part of the gate shutter 18.

With this arrangement, deposits are accumulated only in a region of thegate shutter 18 close to the opening of the inner chamber 17 underplasma processing. This enhances the wet maintainability of the device.

The lowermost part of the inner chamber 17 is positioned below the uppersurface of the sample electrode 6. Plasma is generated mainly above theupper surface of the sample electrode 6 so that more deposits areaccumulated above the upper surface of the sample electrode 6. Thisarrangement enhances the wet maintainability of the device.

The driving device 19 includes a motor 28, a rotary body 21 in intimatecontact with a gate shutter 18, and a transmission part for transmittingthe rotary motion of the motor 28 to the rotary body 21. Thisarrangement allows smooth driving of the gate shutter 18. The rotarybody 21 is made of an elastic resin. This suppresses generation ofparticles attributable to rotation of the gate shutter 18. To furtherreduce particles, a magnet coupling may be used.

The inner chamber 17 is fixed to the vacuum chamber 1 by placing a hoodpart projecting outside the cylinder on the upper surface of the vacuumchamber 1. This suppresses generation of particles attributable torotation of the gate shutter 18.

Particles generated at the contact part between the gate shutter 18 orthe inner chamber 17 and the bearing unit 20 and the contact partbetween the gate shutter 18 and the rotary body 21 are blocked by thehood part projecting outside from the cylinder of the inner chamber 17and do not enter the side of the sample 9 and drop below the lowermostpart of the inner chamber 17.

Such an exceptional effect is especially conspicuous in a plasma dopingprocess. In dry etching, deposits accumulated inside a vacuum chamber oran inner chamber is mainly products of an etching reaction and theconcentration of an etchant (radical species in charge of etchingreaction) in plasma rarely changes. In plasma CVD as well as in dryetching, the ratio of a reactive gas taking the initiative in CVDreaction to a gas supplied into a vacuum chamber is generally 10% ormore or at least 3%.

In this case, the concentration of a reaction species in plasma rarelychanges to worse the uniformity of processing in accordance with theamount of deposits accumulated inside a vacuum chamber or an innerchamber. In other words, in case the ratio of a reactive gas (diborane,phosphine, arsine or the like) taking the initiative in reaction ratherthan a rare gas is less than 10% or in particular less than 3% like inplasma doping, the invention is exceptionally advantageous.

Embodiment 2

Embodiment 2 of the invention will be described referring to FIG. 4.FIG. 4 is a cross-sectional view of a plasma-doping device used in theEmbodiment 2 of the invention. Basic configuration in FIG. 4 is the sameas that of Embodiment 1 shown in FIG. 1 although two bearing units 20are respectively arranged in an upper location and a lower location.With this arrangement, the precision of the rotary motion of the gateshutter 18 coaxial with the inner chamber 17 is enhanced. This minimizesthe possibility of the inner wall of the gate shutter 18 coming intocontact with the outer wall of the inner chamber 17 thus suppressinggeneration of particles.

Embodiment 3

Embodiment 3 of the invention will be described referring to FIG. 5.FIG. 5 is a cross-sectional view of a plasma-doping device used in theEmbodiment 3 of the invention with the link part between the innerchamber 17 and the gate shutter 18 being enlarged. In FIG. 5, the innerperiphery of a convex part 29 projecting inside the cylinder of the gateshutter 18 is fitted to a concave part 30 provided outside the cylinderof the inner chamber 17. A bearing unit 20 is provided between theconvex part 29 and the concave part 30. The inner diameter of the convexpart 29 is smaller than the external shape of the cylinder of the innerchamber 17. With this arrangement, it is possible to prevent generationof particles caused by rotation of the gate shutter 17. Particlesgenerated at the contact part between the gate shutter 18 or the innerchamber 17 and the bearing unit 20 due to rotation of the gate shutter17 mostly build up in the concave part 30 provided outside the cylinderof the inner chamber 17 and a dramatically smaller number of particlesdrop between the inner chamber 17 and the gate shutter 18.

Embodiment 4

Embodiment 4 of the invention will be described referring to FIGS. 6through 8. FIG. 6 is a cross-sectional view of a plasma-doping deviceused in Embodiment 4 of the invention. Basic configuration in FIG. 6 isthe same as that of Embodiment 1 shown in FIG. 1 although the vacuumchamber 1 is not cylindrical, the pump 3 as an exhaust device isarranged at the opposite side of the through gate 16, and an innerchamber bottom is provided to the inner chamber 17.

With this arrangement, gas exhaust takes place faster in a region remotefrom the through gate 16 (close to the pump 3). In case plasmaprocessing is made in the absence of the gate shutter 18 or while thegate shutter 18 is placed in an open position, dose appears nonuniformmore conspicuously than Embodiment 1. That is, in such an arrangement,the uniformity improvement effect through plasma processing with thegate shutter 18 in an open position is exceptional.

FIG. 7 is a perspective view of the inner chamber 17 and the gateshutter 18. In FIG. 7, the inner chamber 17 is almost cylindrical but agate opening 31 is arranged in a position corresponding to the throughgate 16 and a window opening 32 is arranged in a position correspondingto a plasma observation window. An inner chamber bottom 33 is a coverfor suppressing buildup of deposits on the bottom of a vacuum chamber.An exhaust opening 34 is an opening for exhausting inside of the vacuumchamber.

The gate shutter 18 has a gate opening 35 arranged in a positioncorresponding to the through gate and a window opening 36 arranged in aposition corresponding to a plasma observation window.

FIG. 7 shows the arrangement in the open position. Arrangement in theclose position is shown in FIG. 8.

The foregoing embodiments only cover part of various variationsconcerning the shape of a vacuum chamber a plasma source system and itsarrangement in the scope of the invention. A variety of other variationsmay be used when the invention is applied.

For example, the coil 8 may have a planar shape. Or, a helicon waveplasma source, a magnetic neutral loop plasma source, a high magneticfield microwave plasma source (electron cyclotron resonance plasmasource) or a parallel planar type plasma source may be used.

Use of an inductive-coupling plasma source makes it easy to form a gasflow-out hole in the surface opposed to a sample (electrode), whichapproach is favorable in terms of device arrangement.

An inert gas other than helium may be used. At least a gas out of neon,argon, krypton, and xenon may be used. Such an inert gas has anadvantage that it causes smaller adverse effects on a sample.

While a sample used in the embodiments is a semiconductor substrate madeof silicon, the invention is applicable to processing of a sample madeof other materials. Note that the invention is an especially usefulplasma doping method in case a sample used is a semiconductor substratemade of silicon.

The plasma doping method is especially useful in case the purities arearsenic, phosphorus, boron, aluminum, or antimony. With thisarrangement, it is possible to manufacture a ultrafine siliconsemiconductor device.

The plasma processing device according to the invention is applicable todry etching and plasma CVD as well as plasma doping.

While the invention has been detailed in terms of its specificembodiments, hose skilled in the art will recognize that various changesand modifications can be made in it without departing the spirit andscope thereof.

The invention is based on the Japanese Patent Application No.2005-099149 filed Mar. 30, 2005 and its content is herein incorporatedas a reference.

INDUSTRIAL APPLICABILITY

A plasma doping method and a plasma processing device according to theinvention provides a plasma doping method excellent in the uniformity ofconcentration of impurities introduced into the surface of a sample anda plasma processing device capable of uniformly performing plasmaprocessing of a sample. The invention is applicable to the impuritydoping process for a semiconductor, manufacture of a thin-filmtransistor used for a liquid crystal, improvement of the surface qualityof various materials and the like.

FIG. 1

-   1: VACUUM CHAMBER-   2: GAS SUPPLY DEVICE-   3: TURBO-MOLECULAR PUMP-   4: PRESSURE REGULATING VALVE-   5: HIGH-FREQUENCY POWER SOURCE FOR A PLASMA SOURCE-   6: SAMPLE ELECTRODE-   7: DIELECTRIC WINDOW-   8: COIL-   9: SUBSTRATE-   10: HIGH-FREQUENCY POWER SOURCE FOR A SAMPLE ELECTRODE-   11: EXHAUST PORT-   12: SUPPORT-   13: GAS INTRODUCTION PATH-   14: GAS MAIN PATH-   15: GAS FLOWOUT HOLE-   16: THROUGH GATE-   17: INNER CHAMBER-   18: GATE SHUTTER-   19: DRIVING DEVICE

1-16. (canceled)
 17. A plasma doping method comprising steps of:transferring a sample into a vacuum chamber via the through gate of thevacuum chamber; mounting the sample on a sample electrode in the vacuumchamber; evacuating the inside of the vacuum chamber while flowing a gastoward the sample almost isotropically from a surface opposed to thesample; generating plasma in the vacuum chamber while controlling theinside of the vacuum chamber at a predetermined pressure; and causingimpurity ions in the plasma to collide with the surface of the sample tointroduce the impurity ions into the surface of the sample; wherein thethrough gate is covered with a gate shutter when plasma is generated.18. The plasma doping method according to claim 17, further comprising astep of: putting a gate shutter that is movable between an open positionwhere the through gate is opened and a close position where the throughgate is covered, into the open position, so as to mount the sample onthe sample electrode in the vacuum chamber; driving the gate shutter byusing a driving device so as to put the gate shutter into the closeposition and cover the through gate, when plasma is generated; andgenerating plasma in the vacuum chamber by supplying a plasma sourcewith a high-frequency power.
 19. The plasma doping method according toclaim 18, wherein the through gate is covered with the gate shutter bydriving the gate shutter into the closed position by utilizing a motor,a rotary body in intimate contact with the gate shutter, and atransmission part so as to transmit the rotary motion of the motor tothe rotary body.
 20. The plasma doping method according to claim 17,wherein said sample is a semiconductor substrate made of silicon; andsaid purities are arsenic, phosphorus, boron, aluminum, or antimony.